Acid Volume Reduction Impact on Slickwater Hydraulic Fracturing Efficiency in Multi-Fractured Unconventional Horizontal Wells

Abstract The objective of this paper is to highlight the results of an acid volume reduction, and elimination study that was performed on multiple unconventional wells, through evaluating various stimulation parameters, and quantifying the differences acid volume has on slick-water stimulation treatment. The assessment depends on the evaluation of different stimulation parameters resulting from the reduction of acid volume at each slick-water hydraulic fracturing stage within a particular well, and extends those understandings to compare offset wells. Impacts on various stimulation parameters such as the Instantaneous Shut-In Pressure (ISIP), net pressure, and perforation efficiency were quantified, then summarized for each batch of stages where a certain acid volume was used, with the overarching goal to quantify the differences on the overall stimulation treatment. The studied wells included an acid volume reduction assessment that was performed in increments of 50%, 75%, and complete acid elimination to achieve a comprehensive evaluation at different acid volumes and when acid is excluded from the stimulation design. At each stimulation stage, average treating pressure, Friction Reducer (FR) concentration, ISIP, and perforation efficiency were the subject of evaluation pertaining measurable parameters used directly for comparison. In general, the overall treatment of stimulation operations was fairly similar for the different acid volume designs used across the application examples highlighted. Similarly, for FR concentration and consumption, reduction in acid volume had no significant impact. ISIP on the other hand, was higher when acid volumes were reduced, and even highest when acid was removed. The final parameter, perforation efficiency, calculated through an in-house developed perforation efficiency estimation tool, yielded consistent improvements when acid was removed. Results from this study yielded a direct quantification of the impacts acid volume reduction has on various stimulation parameters. It was observed that purely from stimulation evaluation, there isn't a negative impact in reducing the volume, on the contrary, eliminating acid yielded stimulation efficiency improvements. The novelty of this paper is that it evaluates the reduction and elimination of acid in slick-water stimulation treatment using cost-free raw stimulation data. The outcomes of this assessment aid significantly in the diagnosis of acid volume reduction within different wells, and identifies optimization opportunities for future applications.